Multiple break electric switch



June 9, 1959 c. R. PETER I 2,890,309

MULTIPLE BREAK ELECTRIC SWITCH Filed June 26, 1957 2 Sheets-Sheet 1 9,4449%). ma l/(co i. 5 am MAM a9 J n 1959 c. R. PETER 2,890,309

MULTIPLE BREAK ELECTRIC SWITCH Filed June 26, 1957 W fl w A /4 22 F5 23 62 24 63 2 Sheets-Sheet 2 52 5 N 5 52 65 5/ N N 5 29' N United States Patent MULTIPLE BREAK ELECTRIC SWITCH Charles R. Peter, New Berlin, Wis., assignor to Allis- Chalmers Manufacturin Company, Milwaukee, Wis.

Application June 26, 1957, Serial No. 668,112

Claims. (Cl. 200104) This invention relates in general to switches and more specifically to electromagnetic contactors used for motor control.

Contactors which are used to control large amounts of current and are subject to frequent operation are generally much larger than is desirable. This is due to the necessity for a device which has sufiicient durability to withstand the high currents and provide maintenance free operation over a substantial period of time. In the past this durability has been achieved by building an oversize contactor. This is generally a satisfactory solution but in certain instances, notably that of traction equipment, space is at a premium and it is not possible to use an oversize contactor. Weight, as well as space, is a limitation on devices used for the control of traction equipment and therefore it is desirable to build a contactor as light as possible without sacrificing durability. In addition, it is also desirable that the contactor be capable of maintenance from a convenient angle to permit easy assembly and disassembly.

This contactor of this invention provides improved operation over the prior art devices through a novel arrangement of the blowout magnets in conjunction with a bridging contact. By locating the blowout magnets in close proximity to the are formed by the interrupted current on separation of the contacts, a rapid blowout action is obtained which lengthens contact life. The magnets may be located very near the contacts since they are made of a highly electrical resistive material and covered with an are resistant glass tape. Such resistive material has the approximate chemical composition of BaFe O The polarity of the magnets is such that the are for one air gap is propelled in a first direction and the arc for the adjoining air gap is propelled in the opposite direction. This permits a closer spacing of the contacts than would otherwise be possible. 7

It is therefore an object of this invention to provide an improved electromagnetic contactor.

It is another object of this invention to provide an electromagnetic contactor using bridging contacts which has an improved blowout action.

It is still another object of this invention to provide an improved electromagnetic contactor in which the contacts may be easily replaced without requiring complete disassembly of the device.

An additional object of this invention is to provide an electromagnetic contactor using permanent magnet arc blowout means in which the flux density across the arc gap is increased by providing a return path for the magnetic flux produced by the permanent magnet blowout means.

Objects and advantages other than those set forth above will be apparent from the following description when read in connection with the accompanying drawings, in which:

Fig. 1 is a front view of an electromagnetic contactor embodying the invention;

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Fig. 2 is a side view of the same contactor as Fig. 1;

Fig. 3 is a plan view of the same contactor as Fig. 1;

Fig. 4 is a sectional view taken along a line IV-IV in Fig. 3 with the interlock switches shown in elevation; and

Fig. 5 is an isometric view of the same contactor as Fig. 1 with parts removed and one fixed contact exploded.

With reference to the accompanying drawings, Figs. 1, 2 and 3 illustrate the outward appearance of a contactor embodying the invention. The electromagnetic actuator 1 of the solenoid type, has an outer casing 2 of magnetic material to which is attached a mounting bracket 3, also of magnetic material. Interlock switches 4 having actuating rods 5 are mounted on the casing 2 by means of brackets 6 and screws 7. These switches provide means for producing the sequential closing of a series of similar contactors. An operating arm 9 fastened to the solenoid plunger 10 by means of a screw 11 operatively connects the plunger to the interlock switch actuating rod. Terminals 12 on the interlock switches provide means for making an electrical connection through the internal contacts of the switches. Terminals 13 provide means for making an electrical connection to the winding of the electromagnetic actuating means. Side members 14 of insulating, are resistant material are fixed to the mounting bracket by means of screws 15 fitting into tapped holes in the side members. A spacer 16 of insulating material separates the side members from the mounting bracket.

The fixed contacts 18, 19, 20 and 21 are held in position by means of bolt members 22, 23, 24 and 25 which pass through the side members and the fixed contacts. The fixed contacts and bolt members are made of nonmagnetic material to avoid reducing the eflectiveness of the blowout magnets. Apertures 27 in the side members adjacent to the air gap between the fixed contacts 18, 19, 20 and 21 and the movable bridging contacts 28 and 29 provide a path for the distended arc. The movable contacts are of nonmagnetic material. Vertical ribs 30 on the side members 14 are used to increase the structural strength of the side member as Well as providing means for increasing the creepage path between the arcs.

Tapped holes 31 in the upper surface of the fixed contacts provide means for connecting the electrical conductors leading to the circuit to be controlled.

With particular reference to Fig. 4, electromagnetic actuator has a movable plunger 10 which is downwardly biased by means of a spring 34 compressed between the operating arm 9 and the removable disk shaped end 35 of the core structure. The removable end of the core structure is held in position against the solenoid winding 37 by means of a retaining ring 38 which fits into a groove 39 in the outer casing of the electromagnetic actuator. A fiber bearing 40 in the removable end portion 35 positions the movable core to allow sliding along the core axis. A similar fiber bearing 41 at the opposite end of the core positions the narrow end of the movable plunger. A pin member 43 passing through the operating arm 9 into the movable plunger prevents the operating arm from rotating on the plunger. A rubber damper 44 contained in a ring in the contact carrier 45 serves to lessen the shock of the contact carrier hitting the insulating spacer. The contact carrier is fastened to the movable plunger by means of a pin 46 passing through the movable plunger 10 and the contact carrier. Also fastened to the contact carrier are the movable bridging contacts 28 and 29 which are held in position by means of nuts 50 and bolts 51. A spring 53 between the contact carrier and the movable contact biases the movable contacts upwardly away from the contact carrier 45.

The hole in the movable contacts through which bolt 51,

passes is slightly oversize to allow a centering action by the movable contacts which resultsin an even distribution of pressure between the fixed contacts.

The contactor uses permanent magnet blowout means located adjacent 'to "the'p'oints' of engagement of the fixed andmovable'contacts. Pernianentmaghets 54 and 55 are located between the fixed'contacts ISand '19. Permanent"magnets 56 and 57'are located between the fixed contacts 20 and 21. For the sake of standardization the magnet means between each of the fixed contacts is made of two similar magnets held together with glass tape. "A single magnet of equivalent size would be equally satisfactory. Magnets 54 and '55 "are assembled with their opposite poles adjoining to present a north pole on the surface adjacent to'fixed contact 18 and a south pole on the surface adjacent to fixed contact 19. Similarly, magnets 56 and 57 are assembled with a north pole on the surface adjoining fixed contact 20 and a south pole on the surface adjoining fixed contact 21. Additional magnets 60 and 61 are located on the outside of the U formed by contacts 18, '19 and 28. Magnet 60 has a south pole adjacent to fixed contact 18 and magnet 61 hasa north pole adjacent to contact 19. Magnets 54, 55, 60 and 61 coact to produce first and second magnetic fields transverse to'the air gaps between movable contact 28 and fixed contacts 18 and 19. It will be noticed that the two magnetic fields are in opposite directions relative to the current flowing in the U. For example, if contact 18 is connected to the positive pole of a current source, an are formed between contacts 18 and 28 will be propelled in a direction into the paper. Since the magnetic field across the gap between contact 19 and 28 is opposite in polarity to the first magnetic field, the are formed across this gap will be propelled in a direction out of the paper.

Similarly, the fixed contacts 20 and 21 are provided with permanent magnet blowout means. Permanent magnets 62 and 63 are located outside of the U formed by contacts 20,21 and 29. Magnet 62 has a south pole adjacent to contact 20 and magnet 63 has a north pole adjacent to contact 21. Magnets 56, 57, 62 and 63 co act to produce third and fourth magnetic fields transverse to the air gaps between movable contact 29 and fixed contacts 20 and 21 respectively. The orientation of the third and fourth fields relative to the air gaps is comparable to the first and second fields in that one are is propelled in a direction into the paper and the other are is propelled in a direction out of the paper upon separation of the contacts.

Separate apertures in the side members have been provided for each point of disengagement of the fixed and movable contacts. Since the side members are made of an are resistant, insulating material, there is no damage to the contactor or no danger of producing a short when the arc is propelled through the aperture and extinguished.

The permanent magnets are covered with a glass tape material 52 to protect the surface of the magnet. The permanent magnets 54, 55, 56 and 57 are prevented from sliding out of their retaining groove by a fiber retainer 64 which is wedged between the fixed contacts. This fiber retainer also serves the purpose of extending the leakage path between the fixed contacts and thereby improving the insulation between them. This is especially important where the location has appreciable amounts of metallic dust in the air.

A flux conductive member 65 of magnetic material joins the adjacent pole faces of magnets 61 and 62. This member is held in 'position by means of horizontal grooves 66 in the inside surfacesof the side members.

. Flux conductive'members 67 and 68 covered with protecti've glass tape 52fit into slots 69 and 70 respectively and join the outer pole faces of magnets 60' and 63 to the mounting bracket 3.

. Members 65, "67 and 68togetherwithmounting bracket 3 provide a low reluctance return path for the flux appearing across the air gaps of the contactor. This greatly increases the strength of the magnetic field in the region of the arc and provides better blowout action.

The flux conductive members 67 and 68 are easily removed by pulling along a line away from the contactor and parallel to the groove in which it slides. Removal of this flux conducting member and the permanent'magnets 54, and 56, 57 between the fixed contacts allows a screwdriver to be inserted between the fixed contacts-and permits removal of the movable contacts 28 and 29 from the contact carrier 45. The fixed contacts 18, 19, 20 and 21 are easily withdrawn from the contactor by removing the respective" bolt member 'and simply sliding the contact upwardly away from the side members.

In this manner any of the contacts may be removed and replaced from the top of the contactor.

Fig. 5 shows more particularly the construction of the fixed contacts and their relation to the 'per'manentma nets and the movable contacts. A notch 71 in the side member 14 is shaped to retain the fixed contact 18 and prevent motion relative to the side member. This retaining means 71 coac'ts with the bolt member 22 to hold the contact in rigid engagement with the'side member. The'permanent magnets 54 and 55, located between the fixed contacts, may he slid 'from the mounting groove byfirst removing the'fiber retainer 64 located between the fixed contacts. A pocket 70 in the side member 14' provides a retaining means for holding the permanent magnet located on the outside of the "contacts. This pocket is typical of the retaining means used to'hold the other magnets on the outside of the U formed by the contacts. Corresponding pockets on the side member which have been removed provide the other halfof "the retaining means. The groove69 shown in the side member 14 allows the flux conducting member of magnetic material to be easily slid into position or removed. This member is held in position solely by the magnetic attraction caused by the flux flowing from magnet 60 through the flux conducting member'67 andthe mounting bracket 3 to the other flux conducting member 68 and the permanent magnet at the opposite end of the contact.

It will be noted that the contactor is symmetrical so that it will interrupt alternating current or direct current of either polarity equally well.

While but one embodiment of the invention has been shown and described, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

What is claimed is:

1. An electromagnetic switch comprising a pair of side members, a first fixed contact of nonmagnetic material, a second fixed contact of nonmagnetic material, a plurality of means holding said fixed contacts in rigid engagement with said side members, a movable contact of nonmagnetic material engageable with said fixed contacts, electromagnetic operating means formoving said movable contact, first magnetic means between said fixed contacts, means holding said first magnetic means in a sliding relation to said side members, removable means restraining said first magnetic means from sliding, second magnetic means adjacent to the point of engagement of said movable contact with said first fixed contact, means holding said second magnetic means ina' fixed relation to said side members, third magnetic means adjacent to the point of engagement of said movable contact with said second fixed contact, means holding said third magnetic means in a fixed relation to' said side members, said magnetic means coacting to produce magnetic flux transverse to the gaps formed on the disengagementof said movable contact from said fixed contact.

2. An electromagnetic switch comprising a pair of side members of insulating, are resistant material, a first fixed contact of nonmagnetic material, a second fixed contact of nonmagnetic material, individual removable means of nonmagnetic material holding said fixed contacts in rigid engagement with said side members, a movable contact of nonmagnetic material engageable with said fixed contacts, electromagnetic operating means for moving said movable contact, first magnetic means between said fixed contacts, means holding said magnetic means in sliding relation to said fixed contacts, removable means restraining said magnetic means from sliding, second magnetic means adjacent to the point of engagement of said first fixed contact and said movable contact, means holding said second magnetic means in a fixed relation to said fixed contacts, third magnetic means adjacent to the point of engagement of said second fixed contact and said movable contact, means holding said third magnetic means in a fixed relation to said fixed contacts, said magnetic means coacting to produce magnetic fields transverse to the are formed at the points of engagement of said movable and said fixed contacts when an electric current is interrupted.

3. An electromagnetic switch comprising a pair of side members of insulating are resistant material, a first fixed contact of nonmagnetic material, a second fixed contact of nonmagnetic material, individual removable means of nonmagnetic material holding said fixed contacts in rigid engagement with said side members, a movable contact of nonmagnetic material engageable with said fixed contacts, electromagnetic operating means for moving said movable contacts, first magnetic means between said fixed contacts, means holding said magnetic means in sliding relation to said fixed contacts, removable means restraining said magnetic means from sliding, second magnetic means adjacent to the point of engagement of said first fixed contact and said movable contact, means holding said second magnetic means in a fixed relation to said fixed contacts, third magnetic means adjacent to the point of engagement of said second fixed contact and said movable contact, means holding said third magnetic means in a fixed relation to said fixed contacts, said magnetic means coacting to produce magnetic fields transverse to the are formed at the points of engagement of said movable and said fixed contacts when an electric current is interrupted, an aperture in said side members adjacent to the points of engagement of said fixed and movable contacts allowing passage of the are formed by an interrupted current and propelled by said magnetic fields.

4. An electromagnetic switch comprising a pair of side members of insulating are resistant material, a first fixed contact of nonmagnetic material, a second fixed contact of nonmagnetic material, individual removable means of nonmagnetic material holding said fixed contacts in rigid engagement with said side members, a movable contact of nonmagnetic material engageable with said fixed contacts, electromagnetic operating means for moving said movable contact, first magnetic means between said fixed contacts, means holding said magnetic means in a sliding relation to said fixed contacts, removable means restraining said magnetic means from sliding, second magnetic means adjacent to the point of engagement of said first fixed contact and said movable contact, means holding said second magnetic means in a fixed relation to said fixed contacts, third magnetic means adjacent to the point of engagement of said second fixed contact and said movable contact, means holding said third magnetic means in a fixed relation to said fixed contacts, said magnetic means coacting to produce magnetic fields transverse to the are formed at the points of disengagement of said movable and said fixed contacts when an electric current is interrupted, an aperture in said side members adjacent to the point of disengagement of said fixed and movable contacts allowing passage of the are formed by an interrupted current and propelled by said magnetic fields, ribs of insulating are resistant material between adjacent apertures.

5. An electromagnetic contactor comprising a. first pair of fixed contacts, a second pair of fixed contacts, a pair of side members of insulating material, a plurality of notches in said side members, said notches opening to the top of said side members and forming retaining means for said fixed contacts, removable bolt members of nonmagnetic material holding said fixed contacts in engagement with said side members, a first movable contact simultaneously engageable with said first pair of fixed contacts, a second movable contact simultaneously engageable with said second pair of fixed contacts, a contact carrier of insulating material, means holding said first and second movable contacts to said contact carrier, means biasing said movable contacts away from said carrier, electromagnetic operating means in engagement with said contact carrier for moving said carrier, said first movable contact having a first point of engagement with one fixed contact of said first pair and a second point of engagement with the other fixed contact of said first pair, said second movable contact having a third point of engagement with one fixed contact of said second pair and a fourth point of engagement with the other fixed contact of said second pair, first magnetic means having a first magnetic pole adjacent to said first point of engagement, second magnetic means having a second magnetic pole opposite in polarity from said first pole, and on the opposite side of said first point of engagement from said first pole, said second magnetic means having a third magnetic pole opposite in polarity from said second pole, and adjacent to the second point of engagement, third magnetic means having a fourth magnetic pole opposite in polarity from said third pole and on the opposite side of said second point of engagement from said third pole, said third magnetic means having a fifth magnetic pole opposite in polarity to said fourth pole and adjacent to the third point of engagement, fourth magnetic means having a sixth magnetic pole opposite in polarity to said fifth magnetic pole and on the opposite side of said third point of engagement from said fifth pole, said fourth magnetic means having a seventh magnetic pole opposite in polarity from said sixth pole and adjacent to the fourth point of engagement, fifth magnetic means having an eighth magnetic pole opposite in polarity to said seventh pole and on the opposite side of said fourth point of engagement from said seventh pole, a plurality of flux conductive members coacting to form a low reluctance magnetic path between said first and fifth magnetic means.

References Cited in the file of this patent UNITED STATES PATENTS Re. 20,094 Wilms et a1. Sept. 1, 1936 731,375 Liggett June 16, 1903 2,239,031 Bierenfeld et a1 Apr. 22, 1941 2,332,446 Heinrich Oct. 19, 1943 2,506,991 Brown May 9, 1950 2,575,060 Matthias Nov. 13, 1951 2,650,971 Dawe Sept. 1, 1953 2,677,032 Wells Apr. 27, 1954 

